silvics and stand dynamics of northern hardwoods and stand dynamics of northern hardwoods outline...
TRANSCRIPT
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
1
Tony D’Amato Rubenstein School of Environment &
Natural ResourcesUniversity of Vermont
Silvics and stand dynamics of northern hardwoods
Outline• Silvics review for primary species in northern
hardwood systems• Historical forest dynamics and structure• Evolution of contemporary forests and
associated challenges • General adaptation considerations
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
2
Silvics of primary species
Silvics of primary speciesSpecies
Shadetolerance
Early relativeheight growth
Relative site requirements
Sugar maple Tolerant Slow to moderate High
American beech Very tolerant Slow Low
Yellow birch Intermediate Moderate Medium to high
Paper birch Intolerant Fast Low
White ash Intermediate Moderate Very high
Red maple Intermediate Moderate Low
Aspen Intolerant Very fast Low
N. red oak Intermediate Moderate Medium
Black cherry Intermediate Fast Low
Red spruce Tolerant Very slow Low
Hemlock Very tolerant Very slow Low
White pine Intermediate Moderate Low
From Leak et al. (2014)
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
3
Stand age 22
Stand age 81
Silvics of primary speciesSpecies Preferred seedbed Gap size
Sugar maple Litter 0.1 ac
American beech Litter 0.1 ac
Yellow birch Humus mix 0.25 ac
Paper birch Humus mix > 1 ac
White ash Litter 0.2 ac
Red maple Litter 0.2 ac
Aspen Moist mineral > 1 ac
N. red oak Litter 0.5 ac
Black cherry Litter > 1 ac
Red spruce Litter, moist mineral 0.1 ac
Hemlock Humus mix 0.1 ac
White pine Moist mineral 0.25 ac
From Anderson et al. (2001)
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
4
Litter quality impacts on sugar maple
Hane
et al. (2003)
57-year-old patch
32-year-old shelterwood
Beech secondary compounds absent
Browse sensitivityPair up with your neighbor and spend a few moments discussing whether or not the following species are browse sensitive:
Probability of medium/high ungulate herbivory risk, 2015. McWilliams et al. (in review)
• American beech• Black cherry• Pin cherry• Striped maple• Sugar maple• White ash• Yellow birch
NoNoYesNoYesYesYes
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
5
Site types and communities
Site types and communities
Thompson et al. (2013)
Just because there is sugar maple in the overstory doesn't mean a site will support a sugar maple-dominated site over time
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
6
Primary forest typesForest type Characteristic
speciesBedrock type Soils
Sugar maple-asha Sugar maple, white ash, basswood
Sugar maple, white ash
Calcareous
Granite, schist
Well- or moderately well-drained tills
Enriched
Northern hardwoodb Beech, sugar maple, yellow birch
Granite, schist Well-to moderately well-drained tills
From Leak et al. (2014)
Site types and communities
NH and VT Natural Communities: aNH=Rich mesic forest; VT=Rich northern hardwood forestbNH=semi-rich mesic sugar maple forest; VT=Northern hardwood forest
Broad scale patterns
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
7
Fine scale patterns
Leak and Riddle (1979)
Northern hardwood dynamics
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
8
Northern hardwood dynamics
Age class
500-year Rotation (Fire 1000 yrs, Wind
1000 yrs)
1364-year Rotation (Fire 3000 yrs, Wind
2500 yrs)
Seedling-sapling (1-15 yrs) 3.0 1.1
Small pole (15-30 yrs) 3.0 1.1
Large pole (30-60 yrs) 6.0 2.2
Mature even-aged (60-100 yrs) 8.0 2.9
Old even-aged (100-150 yrs) 10.0 3.7
Transitional uneven (150-300 yrs) 30.0 11.0
Old uneven-aged (300+ yrs) 40.0 78.0
Expected % of landscape occupied by different age classes based on average, historic disturbance rates (Lorimer and White 2003)
• Lowest frequency of stand-replacing disturbance of any northeast forest type • Average rotation periods of 1000-3000 yrs for stand-replacing wind and fire
Northern hardwood dynamicsGap dynamics (0.5-2.0% of canopy disturbed per year) represent general pattern across northern hardwood forests
Big Reed Forest Preserve, Maine (Fraver et al. 2009)
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
9
Northern hardwood dynamicsNatural age structures• Uneven-aged, but often dominated by
2-3 cohorts• Reflective of moderate disturbance
(30-60% canopy removal) every 60-400 yrs
• Moderate severity events (microbursts, ice) critical for recruiting intolerant and mid-tolerant species
Fraver et al. (2009)
Northern hardwood dynamics• End result: Irregularly structured, multi-cohort forests
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
10
• Live-tree diameter distributions• Rotated sigmoid distribution is most commonly observed
distribution in old-growth stands
Goff and West (1975)Lorimer et al. (2001)
U-shaped mortality trend reinforces this size-structure
Northern hardwood dynamics
• Live-tree diameter distributions• Range of natural distributions documented and
recognized (Leak 1964, 1996; Janowiak et al. 2008)
Natural dynamics and development
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
11
Overstory species dominance over time at gap and stand and scales
Yellow birch, white ash, aspen, sugar maple, pin
cherry, paper birch, beech
Sugar maple, beech, yellow
birch (understory spruce and hemlock)
Beech, sugar maple, yellow birch (some hemlock or
spruce)
Early succession Mid succession Late succession
True stand replacement is rare due to resilience of advance regeneration
General pattern for "matrix" northern hardwoods (semi-rich)
From Thompson and Sorenson (2005)
Rich: Bigtooth aspen, little to no beech
Rich: Basswood, bitternut hickory, white ash
Rich: Basswood, little to no conifer or beech
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
12
Land-use history and contemporaryconditions
Past harvesting practices in northeast US
Kelty and D’Amato 2006
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
13
Early silviculture (vs. harvesting) in northeast US
Increasing demand and transport ability for northern hardwood species in 1900s• 1920-1930s: Establishment of USFS Experimental
Forests in northeastern US (Bartlett ExperimentalForest in 1932)
• Silvicultural research focused on addressingprevailing conditions left from history of land-use
• "Old growth"
• Even-aged
Leak and Yamasaki 2011
General forest conditions
Improvement cutting 60-year-old stand, GMNF 1939 (post-charcoaling)
"Old growth", WMNF (Gilbert and Jensen 1958)
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
14
Changing beech dynamics
Bos
e et
al.
(In
pres
s)
Cale et al. (2017)
Forest age-class conditions
Much of northern hardwood resource is in 61-100 year class• Rarely even-aged due to past selective cutting
but anything but the "balanced condition" early guides were based on
Ducey et al. (2013)
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
15
Downed woody debris
OG SG
Vol
ume
of d
ow
ned
woo
dy d
ebris
(ft3 a
c-1)
0
200
400
600
800
1000
1200
1400
1600
1800
2000Snags
OG SG
Sna
g b
asa
l are
a (f
t2 ac-1
)
0
10
20
30
40
50
Deadwood abundance in current forests
Based on: McGee (2003); Gore and Patterson (1986); Tritton (1980); Kenefic and Nyland (2007); Goodburn and Lorimer (1998)
Selection stands
Selection stands
65-100 yrs
Recent mixedwood dynamics
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
16
Upper ecotone elevation generally shifted downslope
4-5 ft yr-1 from 1991-2010 across 15,000 mi2 area
Foster & D’Amato (2015)
Recent mixedwood dynamics
• Many areas are still recovering from history of selective red spruce harvesting (artificially pushed spruce upslope and out of mixed northern hardwood stands)
• Importance of retaining red spruce on mixedwood sites to provide seed source given slow rates of development
• Prevalence of mixedwood condition often underestimated given current stand conditions on moderate quality sites
Recent mixedwood dynamics
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
17
Adaptation considerations
Adaptation considerationsVulnerability determination for selected forest types in New England and New York (Janowiak et al. in press)Forest type Potential impacts Adaptive capacity Vulnerability
Central hardwoods Moderate-positive Moderate-high Low
Lowland conifer Moderate-negative Moderate Moderate-high
Montane spruce-fir Moderate-negative Low-Moderate Moderate-high
Northern hardwoods Moderate Moderate-high Low-Moderate
Pitch pine-scrub oak Moderate-positive Moderate LowAdaptive capacity of NHW• Positives: many tree species representing broad mix of tolerances and reproductive
strategies; occur across wide range of soils and landforms (some less vulnerable than others)
• Negatives: many species affected or threatened by non-native insects and diseases, deer herbivory
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
18
Adaptation considerationsRevisiting two of several principles guiding previous "new trend" in silvicultural thinking
1. Continuity - provision for continuity in forest structure, function, and biota between pre- and post-harvest (legacies)
2. Complexity - create and maintain structural and compositional complexity and biological diversity through silvicultural treatments
(From Seymour and Hunter 1999, Franklin et al. 2007)
Principle Linkages with Uncertainty and Adaptation
Continuity
• Long-term options for regeneration and structure in face of uncertainty
• Amelioration of harsh environmental conditions• Regeneration safe sites (shaded understory, well-
decomposed dead wood)• Micro-refugia for sensitive taxa
• Conservation of genetic diversity
Adaptation considerationsValue in retention during regeneration harvests
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
19
Principle Linkages with Uncertainty and Adaptation
Complexity
• Reduced vulnerability to disturbance• Heterogeneity in: 1) wind/ice risk, 2) potential host
species abundance, 3) within-species stress tolerance (tree size/age), 4) resource availability
• Multiple recovery/developmental pathways• Diversity of seed sources and reproductive
mechanisms• Heterogeneity in microsites for new species
Adaptation considerationsLook to silvicultural systems that increase within stand and landscape-level complexity
Do we consider artificial regeneration or deliberate tending to increase range of species on these sites?
Decreasing No change Increasing
American beech White ash* BasswoodQuaking aspen Big-tooth aspen N. red oak
Paper birch Eastern white pine Black birchYellow birch Red maple Bitternut hickoryRed spruce Black cherry
Sugar mapleEastern hemlock*
Primarily intolerant and intermediate species
Adaptation considerationsProjected changes in suitable habitat by 2100 Northern Forest region under high emissions scenarios (Janowiak et al. in press)
Northern Hardwoods‐‐Silviculture Institute 9/13/2017
20
• Site and associated natural communities represent most important filter for determining appropriate long-term silviculture regime for northern hardwoods (i.e., listen to Bill)
• Current condition of resource and potential future changes speak to need for applying diversity of regeneration methods that retain and enhance structural and compositional complexity on site
• Group/patch selection, irregular shelterwoods, two-aged variants
Conclusions
THANKS!